Electric circuit breaker with arc current shunting blade stacked on contact blade

ABSTRACT

A movable contact blade of an electric circuit breaker is connected in series with a bimetallic strip forming a part of a tripping device. An arc current shunting blade is stacked on the contact blade, insulated therefrom, and connected to a load terminal strap in shunting relationship to the bimetallic strip. An arc which occurs during interruption of a severe overload current is transferred from the contact blade to the arc current shunting blade, causing the high current to bypass the bimetallic strip.

8 United States Patent Peck 1 Aug. 8, 1972 [54] ELECTRHC CIRCUIT BREAKERWITH 2,1 17,047 5/1938 Wheelock ..200/146 R ARC CURRENT SHUNTING BLADE2,175,827 10/1939 Conklin ..337/41 R STACKED CQNTACT BL DE 2,798,9197/1957 lngwersen ..337/83 R 2,833,888 /1958 Bessiere ..200/146 R X [721Invent: Peck west, 0mm", 3,005,066 10/1961 Powell ..337/83 R x Canada[73] Assignee: Square D. Company Canada Primary Examiner Macon Limited,Toronto Ontario, Canada Attorney-Harold J. Rathbun and Paul J. Rose [22]Filed: May 21, 1971 57 ABSTRACT PP Nod 145,817 A movable contact bladeof an electric circuit breaker is connected in series with a bimetallicstrip forming a s2 u.s.c| ..200/146R 337/41 337/83 P a triWilli;devicearc current shunting 3 6 blade is stacked on the contact blade,insulated [51] Int Cl H01! 33/12 therefrom, and connected to a loadterminal strap in [58] Field 83 shunting relationship to the bimetallicstrip. An arc which occurs during interruption of a severe overloadcurrent is transferred from the contact blade to the [5-6] Referencescued arc current shunting blade, causing the high current to UNITEDSTATES PATENTS yp the bimetallic p- 2,( )55,183 9/1936 Sperry ..337/110R 9 Claims, 6 Drawing Figures PATENTEDAUG 81972 3.683.140

SHEET 1 0F 2 FIG. 2 FIG. 5

INVENTOR. RONALD G. PECK PATENTEDMIB 1972 3.683.140 SHEET 2 BF 2 vINVENTOR.

RONALD G. PECK ELECTRIC CIRCUIT BREAKER WITH ARC CURRENT SHUNTING. BLADESTACKED N CONTACT BLADE This invention is an improvement of the circuitbreaker disclosed in U. S. Pat. No. 3,341,791, issued Sept. 12, 1967, towhich reference may be had for a complete description of the circuitbreaker parts unrelated to the present improvement.

A problem arises in circuit breakers of low rating, because a bimetallicstrip of sufficiently. smallcross section for good response to lowoverload currents is likely to be damaged by severe overload currents.This problem has been solved in thepast by relatively complicatedstructures including a'second set of contacts which close upon incidenceof severe overload current to bypass the current around the bimetallicstrip. The present invention relates to a simple arrangementforbypassing severe overload or'fault currents'around a bimetallic stripwithout the provision of a second set of contacts and separate operatingstructure therefor.

An object of the invention is to provide a simple, inexpensive structurefor'shunting a bimetallic strip of a circuit breaker upon incidence ofsevereoverload or fault currents.

Other objects and advantages will become apparent upon consideration ofthe following specificationalong with the accompanying drawings inwhich:

F IG. 1 is a fragmentary longitudinal-sectional view of a circuitbreaker constructed in accordance withtthe invention, certain portionsbeing omitted for clarity;

FIG. 2 is an enlarged perspective view of an insulator between a contactpressure spring and an arc current shunting blade of this invention;

FIG. 3 is an enlarged perspective view of one of'two insulatingretainers between amovablecontact blade and the arc current shuntingblade of this invention;

FIG. 4 is an enlarged perspective view of the contact pressure spring;

FIG. 5 is an enlarged perspective view of the arc current shuntingblade; and

FIG. 6 is an enlarged perspective view of the-movable contact blade.

With reference to the drawings, FIG. 1 discloses a circuit breaker 10including a load terminal strap 12 having one end of a bimetallic strip14 secured to an inner end thereof. The other end of the bimetallicstrip 14 is connected by a braided wire 16 to a pivotally mounted end ofa movable contact blade l8.having a movable contact 20 secured to theother end thereof for cooperation with a stationary contact 22 securedto a line terminal strap 24 along with an arc runner. 26.

In accordance with the invention, the movable contact blade 18 is shapedas best shown in FIG. 6 and has an arc current shunting blade 28, bestshown in FIG. 5, mounted thereon. The arccurrent shunting blade 28 hasan arcing contact 30 secured to one endthereof. The other end of the arccurrent shunting blade 28 is connected by a braided wire 32 to theloadterminal strap 12 in shunting relationship to the bimetallic strip 14. Atubular insulating sheath 34 is provided on-the wire 32. The blade 28 ismounted on the blade 18 by means of a pair of spool-shaped insulatingretainers 36, one of which is best shown in FIG. 3. Arcuate recesses 18aand 28a (FIGS. 5 and 6) are provided respectively on the blades 18 and28 for reception of one of the retainers 36, and arcuate recesses 18band 28b are proendportion of the bimetallic other and forming an outsidecomer portion of the blade 18. The recesses 28a and 28b are providedrespectively on apair of edge surfaces 28c and 28d exten g substantiallyat right angles to each other and forming aninsidecorner portion of theblade 28 complementary to the outside corner portion of the blade 18.

The blades 18 and 28 are provided respectively with contact mountingsurface 18a and 282 on which the contacts 20 and 30 are'respectivelymounted. The edge surfaces l8eand 28c form equal acute anglesrespectively with the edge surfaces 18d and 28d, and when the blade 28is in mounted position on the blade 18, the edge surfacesl-8e and28e aresubstantially coplanar. The contacts are shaped and mounted in a mannersuch that the contact30 forms a continuation or extension of thecontact20, except for a small air gap between them.

The blade. 28 is'held in positionalso by contact pressure spring 38 bestshown inFIG. by a and having end portions. 38a.and 38b anchored in acrossbar 40 and a transverse. portion 380 bearing on a channel shapedinsulator 42 best shown in'FIG. 2 and mounted in a notch 28fof the blade28.

An are occurring between the contacts 20 and 22 upon opening of thecircuit breaker under severe overload or'fault conditions tends totravel outwardly, to the left as viewed in FIG. 1, whereupon itestablishes itself between the contacts22and 30. The are current at thattime flows through the blade 28 and wire 32, rather than through theblade 18, wire 16, and the bimetallic. strip 14. The bimetallic strip 14is thus protected againstsexcessive. arcing currents.

Other parts of the circuit breaker 10 may be as disclosed in theaforementioned patent. Briefly, upon the occurrence of asustainedmoderate overload, the free strip 14 will move upwardly, as viewed inFIG. 1, to rotate a common trip bar 44 clockwise and release anintermediate latch member 46.for clockwise movement, whereupon a tripmember 48'pivots clockwiseto collapse pairs of toggle .Iink members 49and50. one of which is shown in The link members 50, only FIG. 1, areconnected to a ;driving.bracket52 for the crossbar 40, and collapse ofthe toggle link members causes the crossbar 40 to move the blades 18 and28 and open the contacts 20 and 22.

Upon the occurrence of severe overload or fault currents, the commontrip bar 44 is rotated clockwise instead by an actuating member 54secured to an annature rod 56 carrying anarmature member 58 attractedtowardamagnetic core member 60 upon flow of the excessive currentthrough the load terminal strap 12.

Various modifications may be made in the structure shown and describedwithout departing from the spirit and scope of the invention.

1 claim:

l. Anelectn'c circuit breaker comprising a movable contact blade.connected in series with a bimetallic strip and a terminal strap, andan arc current shunting blade stacked on the movable contact blade,insulated therefrom, and connected to the terminal strap in shuntingrelationship to the bimetallic strip.

2. An electric circuit breaker as claimed in claim 1 including a pair ofmovable contacts mounted respectively on the blades.

3. An electric circuit breaker as claimed in claim 2 including a pair ofspool-shaped insulating retainers insulating the blades from each other.

4. An electric circuit breaker as claimed in claim 3 wherein each bladehas a pair of arcuate recesses and each spool-shaped insulating retaineris received in one recess on one blade and one recess on the otherblade.

5. An electric circuit breaker as claimed in claim 4 wherein the movablecontact blade has a pair of edge surfaces extending substantially atright angles to each other, forming an outside corner portion, and eachhaving one of the arcuate recesses therein, and the are current shuntingblade has a pair of edge surfaces extending substantially at tightangles to each other, forming an inside corner portion complementary tothe outside corner portion of the movable contact blade, and each havingone of the arcuate recesses therein.

6. An electric circuit breaker as claimed in claim 5 wherein each bladehas a contact-mounting edge surface on which its contact is mounted andthe contact-- mounting edge surfaces are substantially coplanar.

7. An electric circuit breaker as claimed in claim 6 wherein thecontact-mounting edge surface of one blade fomis an acute angle with anedge surface thereof mounting edge surfaces are substantially coplanar.

9. An electric circuit breaker as claimed in claim 8 wherein thecontact-mounting edge surface of one blade forms an acute angle withanother edge surface of the respective blade, and the contact-mountingedge surface of the other blade forms on equal acute angle with anotheredge surface of the respective blade.

1. An electric circuit breaker comprising a movable contact bladeconnected in series with a bimetallic strip and a terminal strap, and anarc current shunting blade stacked on the movable contact blade,insulated therefrom, and connected to the terminal strap in shuntingrelationship to the bimetallic strip.
 2. An electric circuit breaker asclaimed in claim 1 including a pair of movable contacts mountedrespectively on the blades.
 3. An electric circuit breaker as claimed inclaim 2 including a pair of spool-shaped insulating retainers insulatingthe blades from each other.
 4. An electric circuit breaker as claimed inclaim 3 wherein each blade has a pair of arcuate recesses and eachspool-shaped insulating retainer is received in one recess on one bladeand one recess on the other blade.
 5. An electric circuit breaker asclaimed in claim 4 wherein the movable contact blade has a pair of edgesurfaces extending substantially at right angles to each other, formingan outside corner portion, and each having one of the arcuate recessestherein, and the arc current shunting blade has a pair of edge surfacesextending substantially at tight angles to each other, forming an insidecorner portion complementary to the outside corner portion of themovable contact blade, and each having one of the arcuate recessestherein.
 6. An electric circuit breaker as claimed in claim 5 whereineach blade has a contact-mounting edge surface on which its contact ismounted and the contact-mounting edge surfaces are substantiallycoplanar.
 7. An electric circuit breaker as claimed in claim 6 whereinthe contact-mounting edge surface of one blade forms an acute angle withan edge surface thereof having one of the arcuate recesses therein, andthe contact-mounting edge surface of the other blade forms an equalacute angle with an edge surface thereof having one of the arcuaterecesses therein.
 8. An electric circuit breaker as claimed in claim 2wherein each blade has a contact-mounting edge surface on which itscontact is mounted and the contact-mounting edge surfaces aresubstantially coplanar.
 9. An electric circuit breaker as claimed inclaim 8 wherein the contact-mounting edge surface of one blade forms anacute angle with another edge surface of the respective blade, and thecontact-mounting edge surface of the other blade forms on equal acuteangle with another edge surface of the respective blade.